Calling Number Delivery (CND), sometimes referred to as "Caller ID" is a Class.SM. feature presently offered by the Regional Bell Operating Companies (RBOCs). This service, which is intended for residential and small business telephone customers, allows Customer Premises Equipment (CPE) devices to receive a calling party's Directory Number (DN) and the date and time of the call during the ringing cycle.
As promoted, CND permits users i.e. called parties, to recognize familiar numbers so as to decide whether to accept the call and, if so, to prepare a response. The CND feature also provides for storage of the directory numbers of the calling parties generally along with the date and time of the call for later retrieval. From a convenience standpoint, the CND feature provides calling parties the ability to determine with limited accuracy who in the called party household the call is likely directed to. Moreover, the feature provides the subscriber with a desired sense of security in that unwanted calls may be readily traced.
As those skilled in the art will recognize, when the CND feature is activated on a line, the calling DN of a terminated call is transmitted along with the date and time to the called party CPE. For an interoffice call, the caller's DN is transferred during the call set-up from the originating Stored Program Control System (SPCS) to which the calling party is connected, to the terminating SPCS to which the called party is connected. The caller's DN is thereafter transmitted along with the date and time of the call, from the terminating SPCS to the called party CPE during the first long silent interval of the ringing cycle, i.e. an interval of silence lasting 3 or more seconds.
Similarly, for an intraoffice call, the caller's DN is retrieved from SPCS memory for transmission to the called party CPE. Then, depending on the options offered by the called party CPE, the DN may be displayed and/or printed out. In alternative arrangements, the called party CPE may be structured to store the DN and date and time for later retrieval by the customer as referenced above. CND is presently offered to users on both a subscription basis and a usage-sensitive basis. The latter requires the CND customer to activate or deactivate the service by going off-hook, awaiting a dial tone and dialing an appropriate activation/deactivation code.
Because CND services require that both the calling party and the called party be in specially-equipped areas to work, situations may arise where the DN of the calling party is not available. In such a case, an out-of-area/DN-unavailable (O/U) indicator, generally signified by the letter "O", along with the date and time will be transmitted to the called party CPE in place of the calling line DN. Similarly, if the calling party DN has been marked to indicate that it is private, the terminating SPCS will not transmit the DN to the called party CPE. This latter option, commonly referred to as Caller Number Delivery."blocking", may generally be selected by the calling party by dialing a specified code (*67 for touch-tone phones, 1167 for rotary/pulse phones) prior to placing the call. Following entry, a stutter dial tone, followed by a second dial tone, is generally provided to confirm the blocking process. Where Calling Number Delivery blocking has been selected, the terminating SPCS will send only the date and time and a privacy indicator, generally signified by the letter "P", to the CPE in place of the calling line DN. This information will indicate to the called party that the calling party has invoked the privacy capability.
As readily seen, the unavailability of CND service in selected calling areas coupled with the ability of perhaps the most undesirable callers to select the "privacy" option and block the transmission of their DN may in many cases defeat the objectives of the CND service. At a minimum, these drawbacks have, to date, hindered widespread consumer acceptance of the service.
Consequently, a need has developed to provide CND service subscribers with a method and system operative to automatically block telephone calls which either because of calling party option and/or unavailability, do not provide the called party with the desired Directory Number of the calling party. Such a method and system should work transparent to the called party so that at the called party's option, calls where the DN has been intentionally blocked are rejected. Alternatively, all calls which do not include DN information--including those where DN is simply unavailable--may be blocked.